Protected connector plug

ABSTRACT

A protected connector plug provided with a hollow, open-end housing; the open end is closed by a single, spring-loaded, slidable sheath surrounding both contact blades and having detents on it to engage a stop in the housing to retain the sheath in the housing. In one embodiment the detents are deflectable to allow the sheath to be inserted after the housing is otherwise complete. In another embodiment the sheath is properly placed within one half of the housing before the other half is joined thereto.

United States Patent [191 Lenkey 1451 Aug. 21, 1973 PROTECTED CONNECTORPLUG [75 inventor: Attila A. Lenkey, Millburn, NJ. [73] Assignee:Lenmark Enterprises, Inc. East Orange, NJ.

[22] Filed: May 19, 1971 21 App]. No.: 144,814

Related US. Application Data [63] Continuation-impart of Ser. No.23,217, March 27,

[52] US. Cl. 339/42, 339/154 [51] Int. Cl H01! 13/44 [58] Field ofSearch 339/36, 40, 42, 154

[5 6] References Cited UNITED STATES PATENTS 3,575,684 4/1971 McIntyre339/42 2,444,843 7/1948 Modrey 339/42 2,082,986 6/1937 Staley 339/422,396,901 3/1946 Tiffany 339/42 FOREIGN PATENTS OR APPLICATIONS 169,52111/1951 Austria 339/42 2/1951 Germany 339/42 8/1936 Switzerland 339/42Primary Examiner-Marvin A. Champion Assistant Examiner-Terrell P. LewisAttorney-Donald P. Gillette 10 Claims, 10 Drawing Figures 3.4 57 2 :e 77 'V- e ,0 f 1 l 151 1 e l l6 i PAIENIEDmsz: ms. 3,754,205

sum 1 or 3 INVENTOR ATTILA A. LENKEY FHW, $314M ATTO NEYS mimemuazn ms3.754.205

SHEEI 3 BF 3 J3 L w M PROTECTED CONNECTOR PLUG This application is acontinuation-in-part of my copending application, Ser. No. 23,217 filedMar. 27, 1970.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to connector plugs with means for shielding against inadvertentcontact with the two blades when the plug is partially inserted into asocket. In particular, it relates to a plug having a sheet thatsurrounds both of the blades and extends transversely between the bladesand is resiliently biased away from the main body of the plug to coverall or most of the blades but is retractable into the body as the bladesare inserted into a socket.

2. Description of the Prior Art The prior art has provided several meansof protecting at least part of the length of the prongs of a male plugwith insulation so that it is difficult or impossible to make conductiveconnection with both prongs when the plug has been inserted far enoughinto a socket to receive current. In some cases, the insulating meanssurrounds and is rigidly attached to each prong. This rigid insulationextends only part way along the length of the prongs and the outermostends of the prongs are reserved as contact areas and are not covered bythe insulation. Such plugs are dependent on the fact that most socketshave their contact portions sufficiently far back from the outer face ofthe socket to engage only the ends of the prongs. However, the contactportions of the socket are not always so far back. It is possible forthe prongs to extend far enough into the socket for the contact portionof the socket to make physical connection only with the insulated partof the prongs of such a plug and thereby conduct no current into theplug itself.

Other prior art structures include telescoping or retractable insulatingmeans separately surrounding each of the blades of a plug and vacantspaces in the body of the plug into which the retractable insulatingmeans can be compressed when the plug is inserted into a socket. Suchprotective devices, if molded as part of the plug body, may lack theresilience necessary to extend over the length of the plug blade oncethey have been compressed for a long time or they may become brittle andwear out easily. If they are entirely separate members, there is apossiblity that they will become dislodged separately and leave one ofthe blades open. If this blade happens to be the one that makes contactwith the hot" line in a socket, it is almost as dangerous as if both ofthe blades were unprotected. Furthermore, such separate protectingsheaths are inherently more complex and have more parts to break thanthe unitary structure of the present invention. In addition, theseparate protective sheaths may become wedged into the contact portionsof the socket and prevent the plug from working. On the other hand, thesingle sheath of the present invention cannot fit into the holesintended to take the prongs of the socket and, therefore, cannot getwedged so as to prevent the socket from working.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a safetyaccording to the present invention;

FIG. 2 is a side elevational view of the plug in FIG.

connector plug FIG. 3 is an exploded sectional view thereof taken alongthe line 3-3 in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line 4-4 in FIG. 2;

FIG. 5 is a cross-sectional view corresponding to FIG. 4 but with thesheath retracted;

FIG. 6 is a cross-sectional view perpendicular to the view in FIGS. 4and 5;

FIG. 7 is a perspective view of the sheath in the previous figures;

FIG. 8 is a rear view of a modified embodiment of a plug constructedaccording to the invention;

FIG. 9 is a cross-sectional view along the line 9-9 in FIG. 8; and

FIG. 10 is a cross-sectional view of the plug in FIG. 9 along the line10-10.

DETAILED DESCRIPTION OF THE INVENTION The safety plug shown in FIGS. l-6has a housing 11 which has an internal, generally rectangular cavity 12.The cavity is open at one end 13 of the housing 11, and it alsocommunicates with top and bottom slots or openings 14 in the housing 11.The top and bottom openings are partially closed by a pair oflongitudinal walls 15, extending therebetween. These walls define tracksbetween themselves and the outer wall of the housing. The tracksslidably receive a bifurcated cover. A tubular integral spring socket 16is formed on the housing 1 1 in the cavity 12 between the walls 15. Apair of contact blades, or prongs, 17 of electrically conductivematerial are attached to the housing 11, which is made of dielectricmaterial. The contact prongs 17 may be attached to the housing 11 in anysuitable manner. By way of illustration, they are shown with offset ends18, with electrical conductive wires 19 attached thereto; the ends 18are molded into the housing 11.

The open end 13 of the housing 11 receives a bifurcated sheath or cover25. The cover 25 has a pair of legs 26 which have internal slots 27which receive the prongs l7 and slide thereon and are joined together atthe outer end by a flat, transverse plate that extends from one of theslots 27 to the other. The cover 25 has a wall 28 connecting the legs26. A single spring 29 in the socket 16 between the walls 15 engages thewall 28 and normally urges the cover 25 out of the housing 11.

A pair of resilient, deflectable detents 30 are formed on the cover 25.The detents have cam surfaces 31 so that they may easily be deflected toenter the housing 11, and then will snap to hold the cover 25 engagedagainst discharge from the housing 11. The detents 36 are spacedsufficiently from the legs 26 to permit the entry of the walls 15between them. The cover 25 is preferably dimensioned so as to at leastpartially sheath the prongs 17, as shown in FIGS. 1, 2, 4 and 6, and toyield to pressure sufficient to overcome the spring 29, to unsheath theprongs 17 as shown in FIG. 5. In this manner, the tips of the prongs 17being exposed, the plug may easily be inserted in the socket and thecover 25 will yield to pressure as the prong enters the socket.

The top and bottom openings 14 in the housing 11 make it possible to geta good grasp on the plug in order to remove it from a socket. Sometimessockets become worn so that their conductive parts bind the prongs, orblades, 17 and make it difficult to pull the plug out of the socket,especially if the plug is made of slick, hard plastic material with notransverse ridges on it. Even with transverse ridges and even if theplug is made of a yieldable material it is still sometimes difficult toremove a plug from the socket in which it has gotten wedged. Suchdifficulties are almost completely obviated by the slotted plug of thepresent invention.

On the other hand, it may be considered undesirable to have a slot thatextends through the main body of the housing 11, and if this is thecase, the housing may be molded in two mirror image sections with flatplate portions that cover the slots 14. If necessary, the height of thedetents 30 may be reduced slightly so as not to rub against the innersurfaces of these plates.

The embodiment shown in FIGS. 1-7 is connected directly to one end of aline cord. The safety features of the invention also make it useful asan attachment to an existing plug. Such an attachment is shown in FIGS.84.0.

FIG. 8 is a rear view of a plug constructed according to the inventionand intended for use as an adjunct to a normal line plug. It has a mainbody portion 32 with grooves 33 therein to make it easier to grasp inorder to pull it out of a socket. At the back end of the plug are twoslotted openings 34 and 36 to receive the prongs of a regular line plug.Within the slots are two contact members 37 and 38, each of which has aconductive tongue 39 and 41, respectively, to engage a regular line pluginserted therein. The body 32 may be made of any of the usual materialsfor making line plugs, including either rigid or slightly deformableinsulating material. Usually the body is molded in two mirror imagesections divided along the horizontal center line of the plug as shownin FIG. 8; The two sections may be joined by ultrasonic welding to forma unitary final structure.

The plug of FIG. 8 is shown in cross-sectional views in FIGS. 9 and 10.The body 32 of the plug has a central cavity 42 with two shelves 43 and44 along the sides thereof. The prongs 46 and 47 each have one end 48and 49, respectively, extending beyond the front surface 51 of the bodyof the plug by the same distance as is customary in normal line plugs.The prongs are held against longitudinal movement by a pair of flanges52 and 53 extending laterally from the prongs 46 and 47, respectively,and fitting into a pair of recesses 54 and 56 in the body 32 of theplug.

While the plug of FIGS. 1-7 was arranged for connection directly to aline cord, the present plug is arranged to have an ordinary line pluginserted in it. For this purpose, the ends 37 and 38 of the prongs 46and 47 extend into the channels 34 and 36, respectively, to makeconnection with a pair of prongs 57 and 58 of a line plug 59. In orderto grip the prongs 57 and 58 firmly, the contact portions 37 and 38 haveshort tongues of the contact material pressed outwardly to engage theprongs 57 and 58.

The male contact ends 48 and 49 of the prongs 46 and 47 are enclosedwithin a sheath 61. This sheath has two channels 62 and 63 to fitloosely around the ends 48 and 49, respectively, and it also has acentral rod 64 molded integrally with the rest of the sheath. The rod 64slides in a channel 66 formed in the body 32 of the plug. Surroundingthe central rod 64 is a spring 67, one end of which presses against theinner surface at the closed outer end 68 of the sheath 61 and the otherend of which fits between the rod 64 and a sleeve 69. The sleeve has aninwardly projecting flange 71 at the end remote from the closed end 68of the sheath 61 and the spring is captured between the closed end 68and the flange 71 and presses the latter against a shoulder 72 thatforms part of the body 32. This spring pressure resiliently forces thesheath 61 to the extended position shown in FIG. 9 in which itcompletely or substantially completely covers both of the blade contactends 48 and 49. In order to limit the outward movement of the sheath 61,it is provided with two ears 73 and 74 that slide along the shelves 43and 44 and engage inwardly projecting stops 76 and 77.

When the plug of FIGS. 8 10 is used as a protective device for anordinary plug, the latter, illustrated by plug 59, is inserted into itand is held more firmly than plugs are usually held in ordinary sockets.This permits the safety plug to be used as the principle device formaking connection with the socket. When the safety plug is inserted intoa socket, the outer end 68 of the sheath first strikes the surface ofthe socket. If the contact ends 48 and 49 of the prongs 46 and 47 areproperly aligned with the usual receptacle portions of the socket, thesafety plug can be pressed forward causing the contact portions 48 and49 to enter the receptacle slots of the socket. As this occurs, thesheath 61 is pushed into the cavity 42, compressing the spring 67. Theresilient force developed by the spring is not enough to cause the plugto push itself out of the socket but is enough to force the sheath 61out of the cavity 42 when the plug is removed from the socket. As aresult, the contact portions 48 and 49 of the prongs 46 and 47 are neverexposed and anyone either inserting or removing the safety plug of. thisinvention cannot come into contact with the prongs.

What is claimed is:

1. A safety plug comprising:

A. an insulating housing;

B. a pair of contact members, each secured internally within saidhousing and having one end extending from said housing;

C. an insulating sheath slidably held within said housing and enclosingsaid ends of said contact members;

D. a spring; and

E. an insulating wall enclosing said spring within said housing, saidspring having one end bearing against said sheath and the other endagainst said housing to press said sheath out of said housing and intosurrounding relationship with respect to said ends of said contactmembers, said sheath comprising a wall portion extending substantiallybetween said ends of said contact members near the outer tips thereof.

2. The plug of claim 1 in which said sheath comprises detents withinsaid housing and said housing comprises stops to hold said detents, andthereby hold said sheath from becoming disengaged from said housing.

3. The plug of claim 2 in which said housing has slots to receive saiddetents, and one end of said slots forms said stops.

4. The plug of claim 1 in which said sheath is bifurcated and has twofree ends extending into said housmg.

5. The plug of claim 2 in which said detents hold said sheath in onlypartial sheathing position on said contact members.

6. The plug of claim 1 in which the inner ends of said- 6 A. saidcontact members have flanges extending contact with a plug inserted intosaid housing from transversely therefrom intermediate their ends; and thend opposite said sheath. B. said housing comprises recesses to receivesaid 9, Th l f claim 1 comprising, in addition, longi.

flanges whereby both ends of said gon tact members tudinal interiorwalls defining a central space between 8 a l; frele to i g g i i igevlces 5 said contact members to enclose said spring.

' e p c 10. The plug of claim 1 in which said sheath com- A. the ends ofsaid contact members extending from said housing are in the form ofblades Spaced apart prlses, in addition, a central rod extending throughsaid by the proper distance to engage electric outlets; spring andattached to the inner surface of said wall and 10 portion, and saidhousing comprises a channel aligned B. the inner ends of said contactmembers are offset with Said Ce a r to guide the free end thereof.

from said first-named ends by a distance to make

1. A safety plug comprising: A. an insulating housing; B. a pair ofcontact members, each secured internally within said housing and havingone end extending from said housing; C. an insulating sheath slidablyheld within said housing and enclosing said ends of said contactmembers; D. a spring; and E. an insulating wall enclosing said springwithin said housing, said spring having one end bearing against saidsheath and the other end against said housing to press said sheath outof said housing and into surrounding relationship with respect to saidends of said contact members, said sheath comprising a wall portionextending substantially between said ends of said contact members nearthe outer tips thereof.
 2. The plug of claim 1 in which said sheathcomprises detents within said housing and said housing comprises stopsto hold said detents, and thereby hold said sheath from becomingdisengaged from said housing.
 3. The plug of claim 2 in which saidhousing has slots to receive said detents, and one end of said slotsforms said stops.
 4. The plug of claim 1 in which said sheath isbifurcated and has two free ends extending into said housing.
 5. Theplug of claim 2 in which said detents hold said sheath in only partialsheathing position on said contact members.
 6. The plug of claim 1 inwhich the inner ends of said contact members are offset and haveelectric leads attached thereto and are molded within said housing. 7.The plug of claim 1 in which A. said contact members have flangesextending transversely therefrom intermediate their ends; and B. saidhousing comprises recesses to receive said flanges whereby both ends ofsaid contact members are free to engage other contact devices.
 8. Theplug of claim 7 in which A. the ends of said contact members extendingfrom said housing are in the form of blades spaced apart by the properdistance to engage electric outlets; and B. the inner ends of saidcontact members are offset from said first-named ends by a distance tomake contact with a plug inserted into said housing from the endopposite said sheath.
 9. The plug of claim 1 comprising, in addition,longitudinal interior walls defining a central space between saidcontact members to enclose said spring.
 10. The plug of claim 1 in whichsaid sheath comprises, in addition, a central rod extending through saidspring and attached to the inner surface of said wall portion, and saidhousing comprises a channel aligned with said central rod to guide thefree end thereof.